using UnityEngine;

// This class implements simple ghosting type Motion Blur.
// If Extra Blur is selected, the scene will allways be a little blurred,
// as it is scaled to a smaller resolution.
// The effect works by accumulating the previous frames in an accumulation
// texture.
[AddComponentMenu("Image Effects/Motion Blur")]
public class MotionBlur : ImageEffectBase
{
    public float blurAmount = 0.8f;
    public bool extraBlur = false;

    private RenderTexture accumTexture;

    protected new void OnDisable()
    {
        base.OnDisable();
        DestroyImmediate(accumTexture);
    }

    // Called by camera to apply image effect
    void OnRenderImage(RenderTexture source, RenderTexture destination)
    {
        // Create the accumulation texture
        if (accumTexture == null || accumTexture.width != source.width || accumTexture.height != source.height)
        {
            DestroyImmediate(accumTexture);
            accumTexture = new RenderTexture(source.width, source.height, 0);
            accumTexture.hideFlags = HideFlags.HideAndDontSave;
            ImageEffects.Blit(source, accumTexture);
        }

        // If Extra Blur is selected, downscale the texture to 4x4 smaller resolution.
        if (extraBlur)
        {
            RenderTexture blurbuffer = RenderTexture.GetTemporary(source.width / 4, source.height / 4, 0);
            ImageEffects.Blit(accumTexture, blurbuffer);
            ImageEffects.Blit(blurbuffer, accumTexture);
            RenderTexture.ReleaseTemporary(blurbuffer);
        }

        // Clamp the motion blur variable, so it can never leave permanent trails in the image
        blurAmount = Mathf.Clamp(blurAmount, 0.0f, 0.92f);

        // Setup the texture and floating point values in the shader
        material.SetTexture("_MainTex", accumTexture);
        material.SetFloat("_AccumOrig", 1.0F - blurAmount);

        // Render the image using the motion blur shader
        Graphics.Blit(source, accumTexture, material);
        Graphics.Blit(accumTexture, destination);
    }
}